Medical device with stretchable electrode assemblies

ABSTRACT

Medical devices and methods for making and using medical devices are disclosed. An example medical device may include a catheter shaft. An expandable balloon may be coupled to the catheter shaft. The balloon may be capable of shifting between an unexpanded configuration and an expanded configuration. Electrode assemblies with electrical pathways may be coupled to the balloon. The electrical pathways may be capable of shifting between a serpentine configuration when the balloon is unexpanded to a straighter configuration when the balloon is expanded.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Application Ser. No. 61/845,291, filed Jul. 11, 2013, theentirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods formanufacturing medical devices. More particularly, the present disclosurepertains to medical devices for renal nerve ablation.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed formedical use, for example, intravascular use. Some of these devicesinclude guidewires, catheters, and the like. These devices aremanufactured by any one of a variety of different manufacturing methodsand may be used according to any one of a variety of methods. Of theknown medical devices and methods, each has certain advantages anddisadvantages. There is an ongoing need to provide alternative medicaldevices as well as alternative methods for manufacturing and usingmedical devices.

BRIEF SUMMARY

This disclosure provides design, material, manufacturing method, and usealternatives for medical devices. An example medical device includes amedical device for renal nerve ablation. The medical device may includea catheter shaft, an expandable member coupled to the catheter shaft,the expandable member having a proximal region, a distal region, and abody extending therebetween, the expandable member being capable ofmoving between an unexpanded configuration and an expandedconfiguration, and a plurality of electrode assemblies fixedly attachedto the body of the expandable member, the plurality of electrodeassemblies each including a stretchable electrical pathway capable ofexpanding with the expandable member.

In some embodiments, when the expandable member is in the unexpandedconfiguration, the electrical pathways are arranged in a nonlinearconfiguration. The nonlinear configuration may be a serpentine orsinusoidal configuration. When the expandable member is in the expandedconfiguration, the electrical pathways may expand and move toward astraighter configuration.

In some embodiments a medical device for renal nerve ablation includes acatheter shaft, a compliant balloon coupled to the catheter shaft, thecompliant balloon capable of shifting between a deflated configurationand an inflated configuration, and a plurality of electrode assembliesfixedly attached to the compliant balloon, the plurality of electrodeassemblies including a plurality of stretchable electrical pathwayscapable of stretching when the compliant balloon shifts to the inflatedconfiguration, wherein the stretchable electrical pathways are capableof shifting between a nonlinear configuration when the balloon is in thedeflated configuration toward a straighter configuration when theballoon is in the inflated configuration.

In some embodiments, a method for ablating renal nerves includesproviding a medical device, the medical device comprising a cathetershaft, a compliant balloon coupled to the catheter shaft, the compliantballoon capable of shifting between a deflated configuration and aninflated configuration, and a plurality of electrode assemblies fixedlyattached to the compliant balloon, the plurality of electrode assembliesincluding a plurality of stretchable electrical pathways capable ofstretching when the compliant balloon shifts to the inflatedconfiguration, wherein the stretchable electrical pathways are capableof shifting between a nonlinear configuration when the balloon is in thedeflated configuration to a linear configuration when the balloon is inthe inflated configuration. The method may further include advancing themedical device through a blood vessel to a position within a renalartery, inflating the compliant balloon, wherein inflating the compliantballoon shifts the stretchable electrode pathways from the nonlinearconfiguration toward the straighter configuration, activating at leastsome of the electrode assemblies, and deflating the balloon, whereindeflating the balloon shifts the stretchable electrical pathways to thenonlinear configuration.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is a schematic view of an example renal nerve ablation system;

FIG. 2 is a schematic side view of a portion of an illustrative medicaldevice in an expanded configuration;

FIG. 3 is a schematic side view of the medical device of FIG. 2 in anunexpanded configuration; and

FIG. 4 is a schematic view of an example electrode assembly.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

The following description should be read with reference to the drawings,which are not necessarily to scale, wherein like reference numeralsindicate like elements throughout the several views. The detaileddescription and drawings are intended to illustrate but not limit theclaimed invention. Those skilled in the art will recognize that thevarious elements described and/or shown may be arranged in variouscombinations and configurations without departing from the scope of thedisclosure. The detailed description and drawings illustrate exampleembodiments of the claimed invention.

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification. All numeric values are herein assumed to be modifiedby the term “about,” whether or not explicitly indicated. The term“about”, in the context of numeric values, generally refers to a rangeof numbers that one of skill in the art would consider equivalent to therecited value (i.e., having the same function or result). In manyinstances, the term “about” may include numbers that are rounded to thenearest significant figure. Other uses of the term “about” (i.e., in acontext other than numeric values) may be assumed to have their ordinaryand customary definition(s), as understood from and consistent with thecontext of the specification, unless otherwise specified.

The recitation of numerical ranges by endpoints includes all numberswithin that range, including the endpoints (e.g. 1 to 5 includes 1, 1.5,2, 2.75, 3, 3.80, 4, and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment(s) described may include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesare not necessarily referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it would be within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments, whether or not explicitlydescribed, unless clearly stated to the contrary. That is, the variousindividual elements described below, even if not explicitly shown in aparticular combination, are nevertheless contemplated as beingcombinable or arrangeable with each other to form other additionalembodiments or to complement and/or enrich the described embodiment(s),as would be understood by one of ordinary skill in the art.

Certain treatments are aimed at the temporary or permanent interruptionor modification of select nerve function. One example treatment is renalnerve ablation, which is sometimes used to treat conditions such as orrelated to hypertension, congestive heart failure, diabetes, or otherconditions impacted by high blood pressure or salt retention. Thekidneys produce a sympathetic response, which may increase the undesiredretention of water and/or sodium. The result of the sympatheticresponse, for example, may be an increase in blood pressure. Ablatingsome of the nerves running to the kidneys (e.g., disposed adjacent to orotherwise along the renal arteries) may reduce or eliminate thissympathetic response, which may provide a corresponding reduction in theassociated undesired symptoms (e.g., a reduction in blood pressure).

Some embodiments of the present disclosure relate to a power generatingand control apparatus, often for the treatment of targeted tissue inorder to achieve a therapeutic effect. In some embodiments, the targettissue is tissue containing or proximate to nerves, including renalarteries and associated renal nerves. In other embodiments the targettissue is luminal tissue, which may further comprise diseased tissuesuch as that found in arterial disease.

In some embodiments of the present disclosure, the ability to deliverenergy in a targeted dosage may be used for nerve tissue in order toachieve beneficial biologic responses. For example, chronic pain,urologic dysfunction, hypertension, and a wide variety of otherpersistent conditions are known to be affected through the operation ofnervous tissue. For example, it is known that chronic hypertension thatmay not be responsive to medication may be improved or eliminated bydisabling excessive nerve activity proximate to the renal arteries. Itis also known that nervous tissue does not naturally possessregenerative characteristics. Therefore it may be possible tobeneficially affect excessive nerve activity by disrupting theconductive pathway of the nervous tissue. When disrupting nerveconductive pathways, it is particularly advantageous to avoid damage toneighboring nerves or organ tissue. The ability to direct and controlenergy dosage is well-suited to the treatment of nerve tissue. Whetherin a heating or ablating energy dosage, the precise control of energydelivery as described and disclosed herein may be directed to the nervetissue. Moreover, directed application of energy may suffice to target anerve without the need to be in exact contact, as would be required whenusing a typical ablation probe. For example, eccentric heating may beapplied at a temperature high enough to denature nerve tissue withoutcausing ablation and without requiring the piercing of luminal tissue.However, it may also be desirable to configure the energy deliverysurface of the present disclosure to pierce tissue and deliver ablatingenergy similar to an ablation probe with the exact energy dosage beingcontrolled by a power control and generation apparatus.

Electrical energy dissipation may rely on electrode impedance or on theimpedance of the electrode-tissue interface rather than dissipation fromthe impedance of tissue between active and ground electrodes.Illustratively, whereas typical RF ablation therapies may use medicaldevices with conductive electrodes, the disclosed concept may includeresistive flexible electrode assemblies including one or more ofresistive electrodes, a resistive material coated on conductiveelectrodes, microheaters, and/or other resistors. The use of resistiveflexible electrode assemblies, may allow for low voltage ablationdevices, where the electrical energy may be provided via direct currentor alternating current (e.g., low voltage direct current, low frequency(less than 200 KHz) alternating current, or other energy).

In some embodiments, efficacy of the denervation treatment can beassessed by measurement before, during, and/or after the treatment totailor one or more parameters of the treatment to the particular patientor to identify the need for additional treatments. For instance, adenervation system may include functionality for assessing whether atreatment has caused or is causing a reduction in neural activity in atarget or proximate tissue, which may provide feedback for adjustingparameters of the treatment or indicate the necessity for additionaltreatments.

While the devices and methods described herein are discussed relative torenal nerve ablation and/or modulation, it is contemplated that thedevices and methods may be used in other treatment locations and/orapplications where nerve modulation and/or other tissue modulationincluding heating, activation, blocking, disrupting, or ablation aredesired, such as, but not limited to: blood vessels, urinary vessels, orin other tissues via trocar and cannula access. For example, the devicesand methods described herein can be applied to hyperplastic tissueablation, cardiac ablation, pulmonary vein isolation, pulmonary veinablation, tumor ablation, benign prostatic hyperplasia therapy, nerveexcitation or blocking or ablation, modulation of muscle activity,hyperthermia or other warming of tissues, ablation within lymphaticvessels or nodes, etc.

FIG. 1 is a schematic view of an example renal nerve ablation system100. System 100 may include a renal nerve ablation device 120. Renalnerve ablation device 120 may be used to ablate nerves (e.g., renalnerves) disposed adjacent to the kidney K (e.g., renal nerves disposedabout a renal artery RA). In use, renal nerve ablation device 120 may beadvanced through a blood vessel such as the aorta A to a position withinthe renal artery RA. This may include advancing renal nerve ablationdevice 120 through a guide sheath or catheter 14. When positioned asdesired, renal nerve ablation device 120 may be activated to activateone or more electrodes (not shown). This may include operativelycoupling renal nerve ablation device 120 to a control unit 110, whichmay include an RF generator, so as to supply the desired activationenergy to the electrodes. For example, renal nerve ablation device 120may include a wire or conductive member 18 with a connector 20 that canbe connected to a connector 22 on the control unit 110 and/or a wire 24coupled to the control unit 110. In at least some embodiments, thecontrol unit 110 may also be utilized to supply/receive the appropriateelectrical energy and/or signal to activate one or more sensors disposedat or near a distal end of renal nerve ablation device 120. Whensuitably activated, the electrodes may be capable of ablating tissue(e.g., renal nerves) as described below and the sensors may be used todetect desired physical and/or biological parameters.

In some embodiments, the renal nerve ablation device 120 may include anelongate tubular member or catheter shaft 122. In some embodiments, theelongate tubular member or catheter shaft 122 may be configured to beslidingly advanced over a guidewire or other elongate medical device toa target site. In some embodiments, the elongate tubular member orcatheter shaft 122 may be configured to be slidingly advanced within aguide sheath or catheter 14 to a target site. In some embodiments, theelongate tubular member or catheter shaft 122 may be configured to beadvanced to a target site over a guidewire, within a guide sheath orcatheter 14, or a combination thereof. An expandable member 130 may bedisposed at, on, about, or near a distal region of the elongate tubularmember or catheter shaft 122, as shown in FIG. 2.

In some embodiments, as shown in FIG. 2, one or more electrodeassemblies 140 may be arranged on the expandable member 130, shown herein an expanded state. The electrode assemblies 140 may be constructed asa flexible substrate attached to the expandable member 130 with one ormore electrodes 145 disposed on the substrate. In at least someembodiments, the electrode assemblies 140 are configured to or otherwisecapable of expanding with the expandable member 130. For example, insome embodiments, the electrode assemblies 140 may be electrodes and/orconductive pathways that are printed directly on the expandable member130. In other embodiments, the electrode assemblies 140 may include asubstrate that is attached to the expandable member 130. When asubstrate is employed, the substrate may be constructed from a polymersuch as polyimide, although other materials are contemplated includingthose disclosed herein.

Each of the electrode assemblies 140 may include one or more discreteelectrical pathways 150, each leading from an electrical contact 155 onan electrode 145 across the expandable member 130. These electricalpathways 150 may include a ground pathway and an active pathway. In someembodiments, a plurality of active pathways may be utilized to power agiven electrode 145. Each of the active pathways may supply a portion ofthe energy used to power the electrode 145. For example, if a givenelectrode 145 is designed to deliver 1 W of power, two electricalpathways 150 that each supply 0.5 W of power may be coupled to theelectrode 145. Analogously, if 1.5 W of power is desired, threeelectrical pathways 150 may be used (each delivering 0.5 W of power). Itcan be appreciated that the distribution of power may be altered so thatthe desired treatment energy can be achieved at the electrodes 145.Furthermore, more or fewer electrical pathways may also be utilized todistribute the desired power.

In at least some embodiments, the total power that can be delivered byeach electrode 145 is substantially equal to the sum of the powersprovided by each electrical pathway 150. Because of this, the powerdelivered by each electrical pathway 150 may be reduced. If furtherreductions in power are desired, additional electrical pathways 150 maybe used. Such arrangements would allow the total power at the electrode145 to be increased while still being able to utilize low powerelectrical pathways 150. Because of this, control unit 112 may only needto supply a relatively low amount of power. This may also allow thepower source to utilize current as a power source (although alternatingcurrent is also contemplated).

The electrode assemblies 140 may be arranged on the expandable member130 in a variety of configurations. In some embodiments, the electrodeassemblies 140 are offset, as illustrated in FIGS. 2-3. In otherembodiments, the electrode assemblies 140 may be linearly arranged alongthe longitudinal axis of the expandable member 130, aligned alongdiagonal lines, or they may have a helical orientation along the lengthof the expandable member 130. In some embodiments, the helicalorientation of electrode assemblies 140 forms at least one complete (360degree) circumferential loop within the lumen or vessel that theexpandable member 130 is positioned. The electrode assemblies 140 mayprovide heating at a location within the tissue surrounding the bodypassageway without damaging the wall of the body passageway in order todisrupt the nerves located in the tissue surrounding the body passagewaywall. A helical orientation may be desirable to help avoid an increasedrisk of stenosis that may be present when electrodes are disposed withina single plane normal to a longitudinal axis of the body passageway(i.e., a circular electrode or group of electrodes).

In some embodiments, at least one temperature sensor 160 may be disposedon one or more electrode assemblies 140. The temperature sensor 160 mayhave an electrical pathway 150 extending from the sensor 160 and acrossthe expandable member 130. In some embodiments, the temperature sensor160 may be a thermocouple or a thermistor. To help reduce overallthickness, the temperature sensor 160 may be positioned within anopening within the substrate. The temperature sensor 160 may be on anon-tissue contacting side of the electrode assembly 140. Accordingly,the temperature sensor 160 may be captured between the electrodeassembly 140 and the expandable member 130 when incorporated into afinal device, such as ablation device 120. This may be advantageoussince surface-mounted electrical components, like thermistors, typicallyhave sharp edges and corners, which may get caught on tissue andpossibly cause problems in balloon deployment and/or retraction.

In some embodiments, the expandable member 130 is a balloon. In someembodiments, the balloon is a compliant balloon. When a compliantballoon is utilized, tensile and/or other forces may act upon theelectrode assemblies 140 (e.g., the electrical pathways 150) when theballoon 130 is expandable. Such forces could undesirably impact theelectrical pathways 150. Accordingly, the electrode assemblies 140 andelectrical pathways 150 are designed so that they are capable ofstretching or otherwise expanding as the compliant balloon is inflated.In some embodiments, the electrical pathways 150 may be disposeddirectly on or formed within the wall of the compliant balloon 130. Insome embodiments the electrical pathways 150 may be printed on thecompliant balloon 130. The electrical pathways 150 may be disposed onthe balloon 130 in a serpentine or sinusoidal configuration, asillustrated in FIG. 4. As the compliant balloon 130 expands, theserpentine pathways 150 are able to straighten. The serpentineconfiguration of the pathways 150 on the unexpanded balloon 130 providesexcess length or slack in the length of the pathway, allowing for theballoon to expand without breaking or overly distorting the pathways150. The height and/or spacing of the serpentine waves may be adjustedbased on the degree of expansion in the balloon. As illustrated in FIG.2, when the compliant balloon 130 is in an expanded configuration, thepathways 150 may move towards a straighter configuration, reducing theheight of the serpentine waves such that the pathways 150 become morelinear. In some embodiments, the electrical pathways 150 may beincorporated into the wall of the compliant balloon 130 duringmanufacture. In some embodiments, the electrical pathways 150 may beprinted directly on the surface of the balloon 130. In some embodiments,the electrical pathways 150 and electrode assemblies 140 may be attachedto the surface of the compliant balloon 130 such as by using adhesive.

As shown in FIG. 4, the electrode assembly 140 may include a pluralityof electrodes. In some embodiments, the electrode assemblies include atleast two electrodes 145. Each electrode 145 may include at least twoelectrical contacts 155. Each electrical contact 155 may be connected toa serpentine electrical pathway 150. The electrical contacts 155 may bearranged in groups to form a circuit across which electrical energy isdelivered. In some embodiments, six electrical contacts 155 are arrangedin groups of three to form a circuit. In some embodiments, eachelectrode assembly 140 may have radiused corners to reduce tendency tosnag on other devices and/or tissue. The electrode assemblies 140 andthe pathways 150 associated with them may function in a bi-polar ormonopolar mode. In some embodiments, the electrode assembly 140 maydeliver at least one watt when apposed against tissue to deliver adenervation therapy. In some embodiments, such as illustrated in FIG. 4,six electrical contacts 155 are arranged in groups of three electrodes145 with energy delivered across the electrode assembly 140. Eachelectrical contact 155 may deliver approximately 0.5 watt of energy. Theplurality of electrical pathways 150 may allow for a greater total powerdelivery. A plurality of electrodes may be disposed in close proximityto each other, and may vary in size to achieve a desired power delivery.In some embodiments, a plurality of electrodes 145 may be directlyattached to or printed on an expandable member 130, without a substrate.The electrode assemblies 140 or individual electrodes 145 may bearranged on the surface of the expandable member 130 to provide adesired treatment pattern. In some embodiments, the arrangement ofelectrode assemblies 140 and/or individual electrodes 145 and theirassociated electrical pathways 150 is selected to achieve a desiredconfiguration when the expandable member 130 is stretched, buckled,twisted, bent, or otherwise manipulated.

In some embodiments, the renal nerve ablation device 120 may include abipolar electrode pair. When the renal nerve ablation device 120 isenergized, RF energy or other suitable energy may pass from an activeelectrode, through the vessel wall and the target tissue (e.g., renalnerves), to a ground electrode thereby creating a corresponding lesionor lesions along a body passageway within which the expandable member130 has been positioned. The temperature sensor 160 may be positionedbetween the ground electrode and the active electrode. The temperaturesensor 160 may be positioned between the ground electrode and the activeelectrode, and may be configured to monitor the temperature of thetarget tissue, the active and ground electrodes, or both. In someembodiments, the at least one temperature sensor 160 may include aplurality of temperature sensors configured to monitor the temperatureof the target tissue, the active electrodes, the ground electrodes, orany combination thereof, at a plurality of locations along the length ofthe expandable member 130.

The system 100 may be used to perform a method of treatment inaccordance with one non-limiting embodiment of the disclosure. Forexample, the control unit 110 may be operationally coupled to theablation device 120, which may be inserted into a body passageway suchthat an expandable member 130 (having a plurality of electrodeassemblies) may be placed adjacent to a first section of the bodypassageway where therapy is required. Placement of the ablation device120 at the first section of the body passageway where therapy isrequired may be performed according to conventional methods, e.g., overa guidewire under fluoroscopic guidance. Once inserted, the expandablemember 130 may be made to expand from a collapsed delivery configurationto an expanded configuration, for example by pressurizing fluid fromabout 2-10 atm in the case of a balloon. This may cause the electrodesand/or electrode assemblies of the expandable member 130 to come intocontact with the first section of the body passageway.

In some embodiments, the ablation device 120 may be advanced through ablood vessel to a position adjacent to a target tissue (e.g., within arenal artery). In some embodiments, the target tissue may be one or morerenal nerves disposed about the renal artery. When suitably positioned,expandable member 130 may be expanded from a collapsed deliveryconfiguration to an expanded configuration. This may place the activeelectrodes against the wall of the blood vessel. The electrodes 145 maybe activated. Ablation energy may be transmitted from the electrodes 145through the target tissue (where renal nerves may be ablated, modulated,or otherwise impacted).

The materials that can be used for the various components of theablation device 120 (and/or other devices disclosed herein) may includethose commonly associated with medical devices. For simplicity purposes,the following discussion makes reference to the ablation device 120.However, this is not intended to limit the devices and methods describedherein, as the discussion may be applied to other similar tubularmembers and/or expandable members and/or components of tubular membersand/or expandable members disclosed herein.

The ablation device 120 and the various components thereof may be madefrom a metal, metal alloy, polymer (some examples of which are disclosedbelow), a metal-polymer composite, ceramics, combinations thereof, andthe like, or other suitable material. Some examples of suitable polymersmay include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene(ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, forexample, DELRIN® available from DuPont), polyether block ester,polyurethane (for example, Polyurethane 85A), polypropylene (PP),polyvinylchloride (PVC), polyether-ester (for example, ARNITEL®available from DSM Engineering Plastics), ether or ester basedcopolymers (for example, butylene/poly(alkylene ether) phthalate and/orother polyester elastomers such as HYTREL® available from DuPont),polyamide (for example, DURETHAN® available from Bayer or CRISTAMID®available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA),silicones, polyethylene (PE), Marlex high-density polyethylene, Marlexlow-density polyethylene, linear low density polyethylene (for exampleREXELL®), polyester, polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polytrimethylene terephthalate, polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide(PPO), poly paraphenylene terephthalamide (for example, KEVLAR®),polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMSAmerican Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinylalcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments the sheath can be blendedwith a liquid crystal polymer (LCP). For example, the mixture cancontain up to about 6 percent LCP.

Some examples of suitable metals and metal alloys include stainlesssteel, such as 304V, 304L, and 316LV stainless steel; mild steel;nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys,and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL®400, NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

As alluded to herein, within the family of commercially availablenickel-titanium or nitinol alloys, is a category designated “linearelastic” or “non-super-elastic” which, although may be similar inchemistry to conventional shape memory and super elastic varieties, mayexhibit distinct and useful mechanical properties. Linear elastic and/ornon-super-elastic nitinol may be distinguished from super elasticnitinol in that the linear elastic and/or non-super-elastic nitinol doesnot display a substantial “superelastic plateau” or “flag region” in itsstress/strain curve like super elastic nitinol does. Instead, in thelinear elastic and/or non-super-elastic nitinol, as recoverable strainincreases, the stress continues to increase in a substantially linear,or a somewhat, but not necessarily entirely linear relationship untilplastic deformation begins or at least in a relationship that is morelinear that the super elastic plateau and/or flag region that may beseen with super elastic nitinol. Thus, for the purposes of thisdisclosure linear elastic and/or non-super-elastic nitinol may also betermed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may alsobe distinguishable from super elastic nitinol in that linear elasticand/or non-super-elastic nitinol may accept up to about 2-5% strainwhile remaining substantially elastic (e.g., before plasticallydeforming) whereas super elastic nitinol may accept up to about 8%strain before plastically deforming. Both of these materials can bedistinguished from other linear elastic materials such as stainlesssteel (that can also can be distinguished based on its composition),which may accept only about 0.2 to 0.44 percent strain beforeplastically deforming.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy is an alloy that does not show anymartensite/austenite phase changes that are detectable by differentialscanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA)analysis over a large temperature range. For example, in someembodiments, there may be no martensite/austenite phase changesdetectable by DSC and DMTA analysis in the range of about −60 degreesCelsius (° C.) to about 120° C. in the linear elastic and/ornon-super-elastic nickel-titanium alloy. The mechanical bendingproperties of such material may therefore be generally inert to theeffect of temperature over this very broad range of temperature. In someembodiments, the mechanical bending properties of the linear elasticand/or non-super-elastic nickel-titanium alloy at ambient or roomtemperature are substantially the same as the mechanical properties atbody temperature, for example, in that they do not display asuper-elastic plateau and/or flag region. In other words, across a broadtemperature range, the linear elastic and/or non-super-elasticnickel-titanium alloy maintains its linear elastic and/ornon-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy may be in the range of about 50 to about 60 weightpercent nickel, with the remainder being essentially titanium. In someembodiments, the composition is in the range of about 54 to about 57weight percent nickel. One example of a suitable nickel-titanium alloyis FHP-NT alloy commercially available from Furukawa Techno Material Co.of Kanagawa, Japan. Some examples of nickel titanium alloys aredisclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which areincorporated herein by reference. Other suitable materials may includeULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available fromToyota). In some other embodiments, a superelastic alloy, for example asuperelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions of the ablation device 120 mayalso be doped with, made of, or otherwise include a radiopaque material.Radiopaque materials are understood to be materials capable of producinga relatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of the ablation device 120 in determining its location. Someexamples of radiopaque materials can include, but are not limited to,gold, platinum, palladium, tantalum, tungsten alloy, polymer materialloaded with a radiopaque filler, and the like. Additionally, otherradiopaque marker bands and/or coils may also be incorporated into thedesign of the ablation device 120 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility may be imparted into the ablation device 120. For example,portions of device, may be made of a material that does notsubstantially distort the image and create substantial artifacts (i.e.,gaps in the image). Certain ferromagnetic materials, for example, maynot be suitable because they may create artifacts in an MRI image. Insome of these and in other embodiments, portions of the ablation device120 may also be made from a material that the MRI machine can image.Some materials that exhibit these characteristics include, for example,tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such asELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenumalloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, andthe like, and others.

U.S. patent application Ser. No. 13/750,879, published as U.S. PatentApplication Pub. No. US 2013/0165926, filed on Jan. 25, 2013, andentitled “METHODS AND APPARATUSES FOR REMODELING TISSUE OF OR ADJACENTTO A BODY PASSAGE” is herein incorporated by reference.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A medical device for renal nerve ablation,comprising: a catheter shaft; an expandable member coupled to thecatheter shaft, the expandable member having a proximal region, a distalregion, and a body extending therebetween, the expandable member beingcapable of moving between an unexpanded configuration and an expandedconfiguration; and a plurality of electrode assemblies fixedly attachedto the body of the expandable member, the plurality of electrodeassemblies each including a stretchable electrical pathway capable ofexpanding with the expandable member.
 2. The medical device of claim 1,wherein the expandable member is a balloon.
 3. The medical device ofclaim 2, wherein the balloon is a compliant balloon.
 4. The medicaldevice of claim 1, wherein each of the electrode assemblies includes atleast two electrodes.
 5. The medical device of claim 1, wherein when theexpandable member is in the unexpanded configuration, the electricalpathways are arranged in a nonlinear configuration.
 6. The medicaldevice of any one of claim 5, wherein the nonlinear configurationcomprises a serpentine or sinusoidal configuration.
 7. The medicaldevice of claim 1, wherein when the expandable member is in the expandedconfiguration, the electrical pathways expand and move toward astraighter configuration.
 8. The medical device of claim 1, wherein theelectrode assemblies are printed on the expandable member.
 9. Themedical device of claim 1, wherein at least some of the electrodeassemblies include a pair of adjacent bipolar electrodes.
 10. Themedical device of claim 1, wherein at least some of the electrodeassemblies include a monopolar electrode.
 11. The medical device ofclaim 1, further comprising a temperature sensor disposed on one or moreof the plurality of electrode assemblies.
 12. The medical device ofclaim 1, wherein the plurality of electrode assemblies are helicallyarranged about the body of the expandable member.
 13. A medical devicefor renal nerve ablation, comprising: a catheter shaft; a compliantballoon coupled to the catheter shaft, the compliant balloon capable ofshifting between a deflated configuration and an inflated configuration;and a plurality of electrode assemblies fixedly attached to thecompliant balloon, the plurality of electrode assemblies including aplurality of stretchable electrical pathways capable of stretching whenthe compliant balloon shifts to the inflated configuration, wherein thestretchable electrical pathways are capable of shifting between anonlinear configuration when the balloon is in the deflatedconfiguration toward a straighter configuration when the balloon is inthe inflated configuration.
 14. The medical device of claim 13, whereinthe stretchable electrical pathways have a serpentine or sinusoidalorientation when in the nonlinear configuration.
 15. The medical deviceof claim 13, wherein the electrode assemblies and the stretchableelectrical pathways are printed directly on the compliant balloon. 16.The medical device of claim 13, further comprising at least onetemperature sensor disposed on the compliant balloon.
 17. The medicaldevice of claim 13, wherein at least some of the plurality of electrodeassemblies include a pair of adjacent bipolar electrodes.
 18. Themedical device of claim 13, wherein at least some of the electrodeassemblies include a resistive member.
 19. The medical device of claim18, wherein the resistive member forms a microheater.
 20. A method forablating renal nerves, the method comprising: providing a medicaldevice, the medical device comprising: a catheter shaft; a compliantballoon coupled to the catheter shaft, the compliant balloon capable ofshifting between a deflated configuration and an inflated configuration,and a plurality of electrode assemblies fixedly attached to thecompliant balloon, the plurality of electrode assemblies including aplurality of stretchable electrical pathways capable of stretching whenthe compliant balloon shifts to the inflated configuration, wherein thestretchable electrical pathways are capable of shifting between anonlinear configuration when the balloon is in the deflatedconfiguration toward a straighter configuration when the balloon is inthe inflated configuration; advancing the medical device through a bloodvessel to a position within a renal artery; inflating the compliantballoon; wherein inflating the compliant balloon shifts the stretchableelectrical pathways from the nonlinear configuration toward thestraighter configuration; activating at least some of the electrodeassemblies; and deflating the balloon; wherein deflating the balloonshifts the stretchable electrical pathways to the nonlinearconfiguration.